Quartz is diamagnetic; however, magnetic fields can affect magnetic materials
in the crystal unit's mounting structure, electrodes, and enclosure. Time-varying
electric fields will induce eddy currents in the metallic parts. Magnetic fields
can also affect components such as inductors in the oscillator circuitry. When
a crystal oscillator is designed to minimize the effects of magnetic fields,
the sensitivity can be much less than 10-10 per oersted. Magnetic-field
sensitivities on the order of 10-12 per oersted have been measured
in crystal units designed specifically for low magnetic-field sensitivity [32].